<?php
/*
 *  $Id$
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * and is licensed under the LGPL. For more information, see
 * <http://www.doctrine-project.org>.
 */

namespace Doctrine\ORM\Query\Expr;

/**
 * Abstract base Expr class for building DQL parts
 *
 * @license http://www.opensource.org/licenses/lgpl-license.php LGPL
 * @link    www.doctrine-project.org
 * @since   2.0
 * @version $Revision$
 * @author  Guilherme Blanco <guilhermeblanco@hotmail.com>
 * @author  Jonathan Wage <jonwage@gmail.com>
 * @author  Roman Borschel <roman@code-factory.org>
 */
abstract class Base {
	protected $_preSeparator = '(';
	protected $_separator = ', ';
	protected $_postSeparator = ')';
	protected $_allowedClasses = array();
	
	private $_parts = array();
	
	public function __construct($args = array()) {
		$this->addMultiple( $args );
	}
	
	public function addMultiple($args = array()) {
		foreach( ( array ) $args as $arg ) {
			$this->add( $arg );
		}
	}
	
	public function add($arg) {
		if( !empty( $arg ) || ($arg instanceof self && $arg->count() > 0) ) {
			// If we decide to keep Expr\Base instances, we can use this check
			if( !is_string( $arg ) ) {
				$class = get_class( $arg );
				
				if( !in_array( $class, $this->_allowedClasses ) ) {
					throw new \InvalidArgumentException( "Expression of type '$class' not allowed in this context." );
				}
			}
			
			$this->_parts[] = $arg;
		}
	}
	
	public function count() {
		return count( $this->_parts );
	}
	
	public function __toString() {
		if( $this->count() == 1 ) {
			return ( string ) $this->_parts[0];
		}
		
		return $this->_preSeparator . implode( $this->_separator, $this->_parts ) . $this->_postSeparator;
	}
}